1. Field of the Invention
The present invention relates to a protective switching apparatus of the circut breaker kind including in as isolating case an interruptible current path in which is disposed at least one pair of cooperating contacts one of which is fixed and the other of which is mobile in response to the actuation either of an electromagnetic or thermal tripping member, or of a voluntary tripping member, via a lock.
2. Description of the Prior Art
As is known from the French patent application No. 84 19043 filed on the Dec. 13, 1984 in the name of the applicant for: "Protective switching apparatus", the mobile contact of the circuit breaker is disposed at a first end of a contact carrying rocker arm made from an electrically conducting material, and the second end of which is associated with a retractable bearing surface forming the outlet member of the lock; in addition, the contact carrying arm is under the control of the action of a resilient means, such as a torsion spring in the form of a hair pin, serving for opening and closing the mobile contact.
In this mechanism, the two particular functions mentioned above, respectively support of the mobile contact and opening-closing of said mobile contact, are fulfilled respectively by two separate mechanical pieces, namely the rocker arm on the one hand and the hair pin spring on the other. However, the fact of using two separate pieces dependent on each other, that is to say acting one on the other, for fulfilling these two functions has the drawback of complicating their relative arrangement for setting and tripping the circuit breaker.
On the other hand, since the rocker arm of this mechanism is associated, on the side of its end opposite that carrying the mobile contact with the lock of the circuit breaker itself associated with the electromagnetic and/or thermal tripper, the current path established between the terminals of the circuit breaker passes then through the whole length of the contact carrying arm, which forms a drawback in that the arm risks being subjected to changes of state, particularly by heating and oxidization, which may result in poor operation of the setting and tripping mechanism of the circuit breaker; to overcome this drawback, problems arise, generally delicate, in the choice of material for the contact carrying rocker arm.